The present invention relates to a method of detecting enclosure leakage of an electrodynamic loudspeaker mounted in a box and a corresponding assembly for detecting enclosure leakage of an enclosure or box of an electrodynamic loudspeaker. Detection of acoustic leakage of an intentionally sealed enclosure of an electrodynamic loudspeaker is highly useful in numerous sound reproduction applications and equipment. It is important to rapidly and reliably detect enclosure leakage because of the associated loss of mechanical stiffness or compliance of the trapped air mass inside the sealed enclosure behind the loudspeaker diaphragm. The loss of stiffness leads to markedly increased diaphragm excursion for a given voice coil voltage, i.e. for a given level of the audio signal. The increase of diaphragm excursion is likely to force the diaphragm and voice coil assembly of the loudspeaker beyond its maximum allowable peak excursion leading to various kinds of irreversible mechanical damage to the loudspeaker. The user will typically notice this kind of irreversible mechanical damage of the loudspeaker due to a grossly distorted sound quality of the loudspeaker or a complete absence of audible sound.
This problem is of significant importance in numerous areas of loudspeaker technology, but in particular in miniature loudspeakers for portable communication devices such as mobile phones and smartphones. In the latter type of devices, a miniature electrodynamic loudspeaker is often mounted in a small sealed enclosure or chamber for example having a volume of about 1 cm3. The way users handle mobile phones and smartphones makes it unavoidable that these occasionally are dropped. These accidental drops may, depending on the impact surface and drop height, lead to severe impact blows on the phone housing or casing. Experience shows that these impacts often are sufficiently large to break a small hole of crack in the small sealed enclosure of the miniature loudspeaker leading to the undesired acoustic leakage. While the costs of a replacement miniature electrodynamic loudspeaker itself are quite modest, the costs of handling the entire repair service procedure are high. This is caused by the multitude of operational activities which typically includes various transportation and order tracking activities, disassembling of the communication device, removal of the defective miniature speaker, mounting of a new miniature speaker, testing, re-assembling and returning etc. In addition, the user is left without an often vital communication tool for the duration of the repair procedure. Hence, it is of considerable value to rapidly and reliably detect enclosure leakage and apply proper precautionary measures in the portable communication device to prevent damage to the miniature electrodynamic loudspeaker by limiting the diaphragm excursion to a value below its maximum allowable peak excursion.
Furthermore, it is of significant interest and value to provide a relatively simple method for monitoring and detecting enclosure leakage to avoid excessive expenditure of computational resources of a microprocessor of the portable communication device and/or other hardware resources handling a leakage detection application.